The reasoning is simple … it is directly quoted in the New Testament by Jude (vv.14-15) and themes of the book referenced in 2 Peter 2:1. Also, the first 36 chapters have been considered Scripture in the Ethiopic Coptic Church (a church who ascribes their founder as the Apostle John).
Robert Bagley (MAT, ‘05) transitioned from corporate America to selling books online by starting a Kindle® publishing business. After searching for an audio book version of "The Book of Enoch" without success he collaborated with Audio Oven to professionally produce one. Others works by Bagley include “Beyond the Mother Church: A Theology of Small Group Ministry in the 21st Century.”